In a power supply device of the related art, for example, as disclosed in Patent Literature 1 (not illustrated), a wire harness is urged upward by a metal flat spring while wiring the wire harness in a bent shape in the protector vertically disposed in the sliding door using a synthetic-resin protector formed by a protector base and a protector cover, the wire harness is wired up to a harness supporter on a side near a vehicle body through a lower opening of the protector, and sagging (extra length) of the wire harness at the time when the sliding door is a half-open state is absorbed.
Further, as an arm power supply device of the related art, Patent Literature 2 (not illustrated) discloses that a link arm is rotatably and axially supported on a plate protector base vertically disposed in the sliding door, the link arm is urged upward by a torsion coil spring (spring member), a harness holder is rotatably and axially supported to the link arm, the wire harness is wired along the protector base to the harness holder and fixed thereto and wired from the harness holder to a side near the vehicle body, and a protector cover may be not used.